Freestanding electrode membrane containing recycled materials

Abstract

A method for manufacturing a free-standing electrode film for an energy storage device includes the steps of: preparing a first mixture including at least one electrode active material and at least one fibrillizable binder, wherein the total solids content of the first mixture is greater than 95% by weight; fibrillating the at least one fibrillizable binder in the first mixture by applying a shear force to the first mixture; pressing the first mixture into a first free-standing electrode film; shredding at least a portion of the first free-standing electrode film; preparing a second mixture including the shredded at least a portion of the first free-standing electrode film; applying a shear force to the second mixture; and pressing the second mixture into a second free-standing electrode film. The first mixture may include at least a portion of a previously manufactured free-standing electrode film.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] Not applicable

[0002] [STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT] Not applicable

[0003] 1.Technical Field

[0004] The present disclosure relates generally to the fabrication of energy storage devices such as Li-ion batteries, solid-state batteries, Li-ion capacitors (LICs), and ultracapacitors, and more particularly to a dry process for fabricating electrodes for energy storage devices. [Background technology]

[0005] 2. Related technologies

[0006] With the growing demand for inexpensive energy storage devices, various methods for manufacturing electrodes have been proposed. Among these are so-called "dry" processes that can produce free-standing electrode films while avoiding the costs and drying times associated with solvents and aqueous solutions typically used in slurry coating and extrusion processes. After the free-standing electrode film is produced, it is laminated to a current collector to produce an electrode. When aligning the electrode film with the current collector for lamination, the film may need to be trimmed, and the trimmed pieces may typically be discarded. In addition, some of the electrode film produced may not meet the specifications for the desired energy storage device and may be discarded entirely. The resulting electrode film trimmed pieces and substandard electrode film may become waste and reduce the yield of the manufacturing process. While efforts can be made to increase the efficiency of the manufacturing process to produce less waste, even small amounts of waste can reduce the economic viability of the process, which can have a particularly significant impact if the process is to be used for mass production of energy storage devices. Given the rising prices of raw active materials, the situation will only worsen. Summary of the Invention

[0007] The present disclosure contemplates various systems, methods, and related products for overcoming the above-described shortcomings associated with the related art. One aspect of an embodiment of the present disclosure is a method for manufacturing a freestanding electrode membrane for an energy storage device. The method may include preparing a first mixture including at least one electrode active material and at least one fibrillizable binder, wherein the first mixture has a total solids content greater than 95% by weight. The method may further include fibrillating the at least one fibrillizable binder in the first mixture by applying a shear force to the first mixture, and pressing the first mixture into a first freestanding electrode membrane. The method may further include shredding at least a portion of the first freestanding electrode membrane (e.g., to become recycled material in a subsequent membrane), and preparing a second mixture including at least one electrode active material, at least one fibrillizable binder, and the shredded at least portion of the first freestanding electrode membrane. The method may further include fibrillating the at least one fibrillizable binder in the second mixture by applying a shear force to the second mixture, and pressing the second mixture into a second freestanding electrode film, which may consequently comprise at least a portion of the first freestanding electrode film as recycled material.

[0008] The first mixture can include at least a portion of a previously produced freestanding electrode film. Similarly, a portion of a second freestanding electrode film can be recycled and used in a subsequent mixture to produce a subsequent freestanding electrode film. In this manner, the manufacturing process, whether a batch process or a continuous process, can incorporate recycled material into each successive electrode film produced.

[0009] Preparing the second (and / or first) mixture may include mixing the second (and / or first) mixture, and applying shear force to the second (and / or first) mixture may include mixing the second (and / or first) mixture with a shear force greater than the shear force used to prepare the mixture.

[0010] At least one electrode active material of the first mixture and / or at least one active material of the second mixture may include one or more electrode active materials selected from the group consisting of lithium metal oxides such as lithium nickel cobalt manganese oxide (NCM), lithium iron phosphate (LFP), lithium nickel cobalt aluminum oxide (NCA), lithium manganese nickel oxide (LMNO), lithium manganese iron phosphate (LMFP), lithium manganese oxide (LMO), and lithium cobalt oxide (LCO), carbon-based materials such as graphite, activated carbon, hard carbon, and soft carbon, titanium dioxide, and silicon-based materials. Either or both of the first and second mixtures may include a conductive material, a solvent, a paste, a slurry, a polymer additive, a polymer additive in a liquid carrier, and / or a solid electrolyte powder. The boiling point of the solvent may be below 180°C.

[0011] The chopped at least portion of the first freestanding electrode film may constitute 0.1% to 5%, 5% to 25%, 25% to 50%, 50% to 75%, 75% to 95%, or greater than 95% of the second mixture.

[0012] Another aspect of an embodiment of the present disclosure is a method of manufacturing a freestanding electrode film for an energy storage device. The method may include preparing a first mixture including at least one electrode active material and at least one fibrillizable binder, wherein the total solids content of the first mixture is greater than 95% by weight; fibrillating the at least one fibrillizable binder in the first mixture by applying a shear force to the first mixture; pressing the first mixture into a first freestanding electrode film; chopping at least a portion of the first freestanding electrode film; preparing a second mixture including the chopped at least a portion of the first freestanding electrode film; applying a shear force to the second mixture; and pressing the second mixture into a second freestanding electrode film.

[0013] The first mixture may include at least a portion of a previously produced free-standing electrode film, and a portion of the second free-standing electrode film may be recycled and used in a subsequent mixture to produce a subsequent free-standing electrode film.

[0014] Preparing the second (and / or first) mixture may include mixing the second (and / or first) mixture, and applying shear force to the second (and / or first) mixture may include mixing the second (and / or first) mixture with a shear force greater than the shear force used to prepare the mixture.

[0015] At least one electrode active material of the first mixture and / or at least one active material of the second mixture may comprise one or more electrode active materials selected from the group consisting of lithium metal oxides such as lithium nickel cobalt manganese oxide (NCM), lithium iron phosphate (LFP), lithium nickel cobalt aluminum oxide (NCA), lithium manganese nickel oxide (LMNO), lithium manganese iron phosphate (LMFP), lithium manganese oxide (LMO), and lithium cobalt oxide (LCO), carbon-based materials such as graphite, activated carbon, hard carbon, and soft carbon, titanium dioxide, and silicon-based materials. Either or both of the first and second mixtures may comprise a conductive material, a solvent, a paste, a slurry, a polymer additive, a polymer additive in a liquid carrier, and / or a solid electrolyte powder.

[0016] The chopped at least portion of the first freestanding electrode film may comprise 0.1% to 5%, 5% to 25%, 25% to 50%, 50% to 75%, 75% to 95%, or greater than 95% of the second mixture. The chopped at least portion of the first freestanding electrode film may comprise 100% of the second mixture. The at least one chopped portion of the first freestanding electrode film may comprise only the electrode active material contained in the second mixture.

[0017] Another aspect of an embodiment of the present disclosure is a method of manufacturing an energy storage device, which may include either of the above methods of manufacturing a freestanding electrode film, plus laminating the second freestanding electrode film onto a current collector. (If the first freestanding electrode film is within specifications and is merely trimmed to generate recycled material, the first freestanding electrode film may similarly be laminated onto a current collector to manufacture an energy storage device.)

[0018] Another aspect of an embodiment of the present disclosure is a free-standing electrode film for an energy storage device, which may include at least one electrode active material; and at least one fibrillizable binder, wherein at least a portion of the at least one electrode active material and at least a portion of the at least one fibrillizable binder are recycled from shredded electrode film.

[0019] The total binder content of the freestanding electrode film may be less than 8%, less than 4%, less than 3%, or less than 2% by weight of the freestanding electrode film. [Brief explanation of the drawings]

[0020] These and other features and advantages of the various embodiments disclosed herein will be better understood with regard to the following description and drawings, in which like numerals refer to like parts throughout.

[0021] [Figure 1] 1 illustrates a system for manufacturing an electrode for an energy storage device according to an embodiment of the present disclosure.

[0022] [Figure 2] 1 illustrates an operational flow for manufacturing an electrode for an energy storage device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present disclosure encompasses various embodiments of a system for manufacturing electrodes for energy storage devices, as well as methods of manufacture and intermediate and final products thereof. The detailed description set forth below in connection with the accompanying drawings is intended as a description of some currently contemplated embodiments and is not intended to represent the only manner in which the disclosed invention may be developed or utilized. The description describes functions and features in connection with the illustrated embodiments. However, it should be understood that the same or equivalent functions may be achieved by different embodiments that are also intended to be encompassed within the scope of the present disclosure. It should be further understood that the use of relational terms such as first and second is used only to distinguish one entity from another and does not necessarily require or imply any actual relationship or order between such entities.

[0024] FIG. 1 illustrates a system 100 for manufacturing electrodes for energy storage devices, such as Li-ion batteries, solid-state batteries, Li-ion capacitors (LICs), or ultracapacitors. A completed energy storage device may include one or more electrodes made by the disclosed methods, where each electrode may be assembled by laminating one or more free-standing electrode films onto a current collector, such as an aluminum metal sheet (for a cathode electrode) or a copper metal sheet (for an anode electrode). As shown schematically in FIG. 1 , the system 100 may generally include a premixer 110 for preparing a dry mixture of the components of the electrode film to be produced, a high-shear mixer 120 for applying shear force to the mixture, a press 130 for pressing the dry mixture into a free-standing electrode film, and a laminator 140 for laminating the free-standing electrode film onto a current collector, resulting in an electrode. Unlike conventional systems, the exemplary system 100 shown in FIG. 1 provides for recycling any unused portions of electrode film output by the press 130 or laminator 140, such as off-spec electrode film produced from the dry mix or electrode film trimmings that may otherwise be removed from usable electrode film as part of the lamination process. Such unused portions of electrode film may be shredded by a shredder 150, as shown schematically in FIG. 1, returned to the premixer 110, and incorporated into the dry mix to be used to produce subsequent electrode films. In this manner, continuous or batch manufacturing processes may be implemented that substantially eliminate electrode film waste while mitigating process efficiency considerations. As described herein, it has been discovered that using recycled electrode film material according to the disclosed technology does not adversely affect the properties of the resulting electrode or energy storage device, making the disclosed innovation highly advantageous for mass production of energy storage devices.

[0025] 2 , an exemplary operational flow for manufacturing an electrode using system 100 may begin with preparing a first mixture (step 210) including at least one electrode active material and at least one fibrillizable binder. The electrode active material may depend on the particular energy storage device to be fabricated and may include, for example, lithium nickel cobalt manganese oxide (NCM), lithium iron phosphate (LFP), lithium nickel cobalt aluminum oxide (NCA), lithium manganese nickel oxide (LMNO), lithium manganese iron phosphate (LMFP), lithium manganese oxide (LMO), lithium cobalt oxide (LCO), graphite, activated carbon, hard carbon, soft carbon, titanium dioxide, and / or silicon. The at least one fibrillizable binder may include, for example, a thermoplastic binder capable of stretching to become longer and thinner when subjected to a shear force without breaking, such as polytetrafluoroethylene (PTFE). The first mixture may also include additional binders (fibrillizable or otherwise), and at least one fibrillizable binder may be a component of a composite binder such as those disclosed in U.S. Patent Application Publication No. 2022 / 0158150, entitled "Dry Electrode Manufacture with Composite Binder," the entire contents of which are incorporated herein by reference. The total binder content in the first mixture may be less than 8%, preferably less than 4%, and more preferably less than 3% or less than 2%.

[0026] The first mixture may further include a conductive material such as activated carbon, a conductive carbon black such as acetylene black, Ketjen black, or Super P (e.g., carbon black sold under the trade name SUPER P® by Imerys Graphite & Carbon, Switzerland), carbon nanotubes (CNTs), graphite particles, graphene, a conductive polymer, and combinations thereof. The conductive material may be an element of a conductive paste comprising a polymer additive mixed with a liquid carrier, as described in U.S. Pat. No. 11,508,956 (the "'956 patent"), entitled "Dry Electrode Manufacture with Lubricated Active Material Mixture," the entire contents of which are incorporated herein by reference. Although not separately shown in FIG. 2 of the present disclosure, an additive solution such as that contemplated in the '956 patent may include a polymer additive mixed with a liquid carrier, without necessarily including a conductive material, and may be added to the first mixture described herein.

[0027] To chemically activate the at least one fibrillizable binder and improve its adhesive strength (e.g., allowing it to further soften and increase its ability to stretch without breaking), the first mixture may include a highly volatile solvent, as described in U.S. Patent No. 9,236,599, entitled "Low Cost High Performance Electrode for Energy Storage Devices and Systems and Method of Making Same," and U.S. Patent No. 10,069,131, entitled "Electrode for Energy Storage Devices and Method of Making Same," each of which is incorporated herein by reference in its entirety. The solvent may have a relatively low boiling point, below 180°C, below 130°C, or below 100°C, thereby requiring minimal or no subsequent drying process to remove the solvent (unlike slurry-based and extrusion processes for producing electrodes). Examples of solvents may include hydrocarbons (e.g., hexane, benzene, toluene), acetates (e.g., methyl acetate, ethyl acetate), alcohols (e.g., propanol, methanol, ethanol, isopropyl alcohol, butanol), glycols, acetone, dimethyl carbonate (DMC), diethyl carbonate (DEC), and tetrachloroethylene. Unlike in slurry-based and extrusion methods, the amount of solvent can generally be very small, for example, the total solids content of the first mixture is greater than 95% by weight.

[0028] When manufacturing an electrode for a solid-state battery, it is contemplated that the first mixture may include a solid electrolyte powder. The solid electrolyte powder may be a dry electrolyte powder, as described in Applicant's co-pending U.S. patent applications Ser. Nos. 17 / 942,458 and 17 / 942,579, entitled "Dry Electrode Manufacture for Solid State Energy Storage Devices," the entire contents of each of which are incorporated herein by reference, and may be primarily (e.g., 80-100% by weight) garnet-structure oxides, such as lithium lanthanum zirconium oxide (LLZO) (e.g., Li ), containing various dopants. 6.5 La3Z r 2O 12 or Li7La3Zr2O 12 ), lithium lanthanum zirconium tantalum oxide (LLZTO) (e.g., Li 6.4 La3Z 1.4 Ta 0.6 O 12 ), lithium lanthanum zirconium niobium oxide (LLZNbO) (e.g., Li 6.5 La3Zr 1.5 Nb 0.5 O 12 ), lithium lanthanum zirconium tungsten oxide (LLZWO) (e.g., Li 6.3 La3Zr 1.65 W 0.35 O 12 ), perovskite structure oxides, for example, lithium lanthanum titanate (LLTO) (for example, Li 0.5 La 0.5 TiO3, Li 0.34 La 0.56 TiO3 or Li 0.29 La 0.57TiO3) or lithium aluminum titanium phosphate (LATP) (e.g., Li 1.4 Al 0.4 Ti 1.6 (PO4)3), lithium superionic conductor Li 2+2x Zn 1-x GeO4 (lithium super ionic conductor: LISICON), for example, lithium aluminum titanium phosphate (LATP) (e.g., Li 1.3 Al 0.3 Ti 1.7 (PO4)3), lithium aluminum germanium phosphate (LAG or sodium superionic conductor, i.e., NASICON-type LAGP) (e.g., Li 1.5 Al 0.5 Ge 1.5 (PO4)3 or Li 1.5 Al 0.5 Ge 1.5 P3O 12 ), or phosphates, such as lithium titanium phosphate (LTPO) (e.g., LiTi2(PO4)3), lithium germanium phosphate (LGPO) (e.g., LiGe2(PO4)3), lithium phosphate (LPO) (e.g., gamma-Li3PO4 or Li7P3O 11), or a ceramic such as lithium phosphorus oxynitride (LiPON). As another example, the solid electrolyte powder can be primarily (e.g., 80-100% by weight) a polymer such as PEO, PEO-PTFE, PEO-LiTFSi, PEO-LiTFSi / LLZO, PEO-LiClO4, PEO-LiClO4 / LLZO, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), polyphenylene oxide (PPO), polyethylene glycol (PEG), polyether-based polymers, polyester-based polymers, nitrile-based polymers, polysiloxane-based polymers, polyurethane, poly(bis((methoxyethoxy)ethoxy)phosphazene) (MEEP), or polyvinyl alcohol (PVA). As another example, the solid electrolyte powder may be primarily (e.g., 80-100% by weight) lithium sulfide (LS) (e.g., LiS), glassy lithium sulfide phosphorus sulfide (LSPS) (e.g., LiS-P2S5), glassy lithium sulfide boron sulfide (LSBS) (e.g., Li2S-B2S3), glassy lithium sulfide silicon sulfide (LSSiS) (e.g., Li2S-SiS2), lithium germanium sulfide (LGS) (e.g., Li4GeS4), lithium phosphorus sulfide (LPS) (e.g., Li3PS4, such as 75Li2S-25P2S5, or Li7P3S, such as 70Li2S-30P2S5). 11 ), lithium silicon phosphorus tin sulfide (LSPTS) (e.g., Li x (SiSn)P y S z), argyrodite Li6PS5X (X = Cl, Br) (e.g., LPSBr such as Li6PS5Br, LPSCl such as Li6PS5Cl, Li6PS5Cl 0.5 Br 0.5 LPS such as ClBr, or Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 LSiPSCl), or thio-LISICON (e.g., Li 10 GePS 12 It may be a sulfide such as LGPS.

[0029] Due to the cyclical nature of the recycling process enabled by system 100, the first mixture contemplated in step 210 of Figure 2 does not necessarily represent an initial run or initial batch of a continuous process. Rather, the first mixture may represent a mixture prepared at any stage in an ongoing process. As such, the first mixture itself may include at least a portion of a previously manufactured free-standing electrode membrane (shown in Figure 1 as "shredded membrane"), as described in more detail below.

[0030] The operational flow of FIG. 2 may continue with applying shear force to the first mixture (step 220). The premixer 110 for preparing the first mixture in step 210 may generally be any type of device for mixing ingredients, such as a hand mixer, a V-blender, or a cone blender. However, the mixer 120 for applying shear force may advantageously be a high-shear mixer, such as a kitchen blender, an industrial blender, a jet mill, or a multi-roll mill (e.g., a two-roll mill, a three-roll mill, etc.), to apply sufficient shear force to fibrillate the fibrillizable binder. In this regard, it is contemplated that preparing the first mixture may include mixing the first mixture, and applying shear force to the first mixture may include mixing the first mixture at a shear force greater than the shear force used to prepare the first mixture. Mixing as part of the preparation of the mixture may be less likely to cause fibrillation than high-shear mixing, and preferably may be substantially free of fibrillation. It should be noted that in some cases, the premixer 110 and the high shear mixer 120 may be the same device, for example, if the same mixer is first operated at one setting (e.g., one speed setting) and then at another setting. It is also contemplated that steps 210 and 220 may overlap to some extent, completing the first mixture after some of the components of the first mixture have already begun to experience shear forces. For example, solvent and / or fibrillizable binder may be injected or otherwise added (or supplemented) to the high shear mixer 120 after high shear mixing has already begun.

[0031] Once the fibrillizable binder is sufficiently fibrillated, which may help ensure that the first mixture has the ability to properly stretch without breaking, the operational flow of FIG. 2 may continue with pressing the first mixture into a first freestanding electrode film (step 230). Press 130 may be a roller press and may typically include horizontally arranged work rolls so that the film emerges from its bottom as the powder mixture is poured onto it to form the film. Heat activation of the fibrillizable binder may be performed earlier in the process or on press 130 (which may be heated), as described in U.S. Patent Application Publication No. 2020 / 0388822, entitled "Dry Electrode Manufacture by Temperature Activation Method," the entire contents of which are incorporated herein by reference. Press 130 may be a component of a mill line, which may further include one or more thickness reduction presses, which may typically include vertically arranged work rolls. Press 130 may feed the finished film to laminator 140. An example of press 130 and laminator 140 is the apparatus described in applicant's U.S. patent application Ser. No. 17 / 835,205, entitled "Free-Standing Electrode Film for Dry Electrode Manufacture," the entire contents of which are incorporated herein by reference.

[0032] In the context of the operational flow of FIG. 2 , this may represent one exemplary iteration of the cyclical recycling process, where the first freestanding electrode film refers to a film that is wholly or partially unusable in an energy storage device and is subsequently recycled (in whole or in part) to produce a second freestanding electrode film into a subsequent second mixture. At this point, the operational flow may continue with shredding at least a portion of the first freestanding electrode film (step 240). An example of a first freestanding electrode film that is wholly unusable is when it is an off-spec film that is a waste output of press 130. An example of a first freestanding electrode film that is partially unusable is when a portion of the film is trimmed during the lamination process or thickness reduction, in which case the unused strip, edge, or other trimmed portion may be a waste output of laminator 140 or press 130. Shredding of such unused membrane or membrane trimmings may be performed by shredder 150 shown in Figure 1, which may be any type of shredder or combination of shredders, such as a paper shredder, a mower, a fitzmill, a horizontal hammer mill, a vertical hammer mill, a low-speed shear shredder, a granulator, a knife hog, a raspberry, a mollusk, a flail, a cracker mill, a refining mill, etc. The recycled material output from such shredding (shown in Figure 1 as "shredded membrane") may then be returned to premixer 110 and incorporated into a subsequent dry mix for subsequent production of free-standing electrode membranes. As a result, the operational flow of FIG. 2 may continue with preparing a second mixture containing shredded electrode film (step 250), applying a shear force to the second mixture (step 260), pressing the second mixture into a second free-standing electrode film (step 270), and laminating the second free-standing electrode film onto a current collector (step 280). Steps 250-270 may be the same as steps 210-230 described above. Note that, although not separately shown in FIG. 2 , step 280 of laminating a second free-standing electrode film onto a current collector (resulting in an electrode) may be performed on the first electrode film, assuming that the first electrode film is a usable film (e.g., if only the trimmed portion is recycled).As with the first mixture, the total binder content in the second mixture (and similarly in either of the freestanding films produced from these mixtures) may be less than 8%, preferably less than 4%, and more preferably less than 3% or less than 2%.

[0033] As noted above, the use of recycled electrode membrane materials according to the disclosed technology has been found to have no adverse effect on the properties of the resulting electrode or energy storage device. Table 1 below provides exemplary data on the electrochemical performance of NCM electrodes made using recycled electrode membranes according to the above process.

[0034] Table 1 [Table 1]

[0035] As can be seen, the discharge capacity and efficiency remain consistent regardless of the relative proportions of pristine and recycled materials. Although not reflected in Table 1, it has been further found that the discharge capacity and efficiency remain consistent for the 0% pristine / 100% recycled material case, and the same is true for C-rates of 0.1, 0.2, 0.5, 1, 2, 3, and 4. As a result, it is anticipated that high power density can be maintained regardless of the amount of recycled membrane material used in the manufacturing process, making this technology suitable for use in cathodes of fast-charging electric vehicle batteries. The recycled membrane can simply be shredded and added directly to the subsequent mixture without any other adjustments to the formulation or manufacturing process. However, it is anticipated that minor adjustments to the formulation or process may be made to closely match the properties.

[0036] As an exemplary anode material, Tables 2.1 and 2.2 below also show average data for the electrochemical performance of graphite electrodes made with recycled electrode films according to the above process.

[0037] Table 2.1 [Table 2]

[0038] Table 2.2 [Table 3]

[0039] Again, the discharge capacity and efficiency remain consistent, at least for the second cycle, regardless of the relative proportions of pristine and recycled material. Although not reflected in Tables 2.1 and 2.2, it has been further found that the discharge capacity and efficiency remain consistent at higher percentages of recycled material (up to and including 0% pristine / 100% recycled). Again, the recycled membrane may simply be shredded and added directly to the subsequent mixture without any other adjustments to the formulation or manufacturing process. However, it is anticipated that slight adjustments to the formulation or process may be made to closely match the properties.

[0040] Tables 3.1, 3.2, and 3.3 below similarly show average data for the electrochemical performance of complete cells containing NCM cathodes and graphite anodes, both made with recycled electrode films according to the process described above.

[0041] Table 3.1 [Table 4]

[0042] Table 3.2 [Table 5]

[0043] Table 3.3 [Table 6]

[0044] Again, as seen above, the discharge capacity and efficiency remain consistent, at least through the second cycle, regardless of the relative proportions of pristine and recycled material. Although not reflected in Tables 3.1, 3.2, and 3.3, it has been further found that the discharge capacity and efficiency remain consistent at higher recycled material percentages (up to and including 0% pristine / 100% recycled material), and the same is true for C-rates of 0.1, 0.2, 0.5, 1.0, and 2.0, where the discharge capacity retention remains consistent for at least 100 cycles. As a result, it is envisioned that high power density can be maintained regardless of the amount of recycled membrane material used in the manufacturing process, making this technology suitable for both the cathode and anode of fast-charging electric vehicle batteries.

[0045] In general, the percentage of recycled material used may depend on the efficiency of the manufacturing process, the available materials, and the needs and objectives of consumers and manufacturers. Any and all percentages of recycled material are contemplated within the scope of the present disclosure, as they have been found to not degrade the quality of the resulting electrode membrane or the resulting electrode. For example, in a highly efficient manufacturing process that produces little waste, the shredded membrane may comprise only 0.1% to 5% by weight of the mixture used to produce the next electrode membrane. In less efficient processes, or if large amounts of discarded electronic membranes (e.g., waste from a manufacturing process that did not use any recycling) are available, higher percentages of shredded membrane may be used, e.g., 5% to 25%, 25% to 50%, 50% to 75%, 75% to 95%, or even greater than 95% (including 100% recycled material in some cases). It is also contemplated that consumers (e.g., electric vehicle manufacturers) may prefer to purchase products containing recycled materials to demonstrate their commitment to reducing waste for the benefit of the environment. In this case, electrodes containing electrode membranes made from "greater than 50% recycled materials" or "100% recycled materials" may be desirable.

[0046] It should be noted that, technically speaking, because recycled membranes themselves contain materials that would be used to produce another electrode membrane, the addition of other materials (e.g., electrode active material, binder, conductive material, solvent, and / or solid electrolyte, as shown in FIG. 1 ) other than the recycled membrane may be considered optional. In this regard, it is contemplated that any of the mixtures described herein may be made from 100% recycled membranes. The fibrillizable binder contained in such shredded membrane material may be refibrillated by applying shear force (e.g., in high shear mixer 120) after being shredded by shredder 150. The refibrillated binder may effectively bind both the electrode active material already contained in the recycled membrane and any new electrode active material (and other components) that may be added to the mixture. As a result, using recycled membranes may reduce the amount of binder required for the mixture, since the recycled membrane itself adds binder to the mixture. On the other hand, it has been found that in some cases, the recycled membrane portion (whether or not it constitutes 100% of the mixture) itself may benefit from the addition of a supplemental fibrillizable binder or solvent, as described above. In particular, when producing activated carbon electrode membranes, especially for capacitors (rather than, for example, NCM battery electrodes), supplementing the recycled portion with a fibrillizable binder and / or solvent may improve the consistency of the resulting electrode membrane.

[0047] The above examples illustrate that the recycled membrane portion of a given dry mix can be produced by shredding off-specification electrode membrane and / or electrode membrane trimmings. However, the use of recycled materials is not necessarily limited to these examples of recycled membranes. Other collected recycled materials that can be added to the mix may include, for example, dry powdery material from a dust collector that may accumulate at any stage of the manufacturing process. It is envisioned that any and all such recyclable materials could be returned to the manufacturing process, potentially reducing waste and yield losses to 0% (compared to the approximately 10% yield loss in a typical slurry-based or extrusion process, or even greater yield losses in a typical dry process that does not use recycled materials).

[0048] The above description is provided by way of example and not by way of limitation. In view of the above disclosure, those skilled in the art will be able to devise variations that fall within the spirit and scope of the invention disclosed herein. Furthermore, the various features of the embodiments disclosed herein can be used alone or in various combinations with each other and are not intended to be limited to the specific combinations described herein. As a result, the scope of the claims is not limited by the embodiments shown.

Claims

1. 1. A method for manufacturing a free-standing electrode film for an energy storage device, the method comprising: preparing a first mixture comprising at least one electrode active material and at least one fibrillizable binder, wherein the total solids content of the first mixture is greater than 95% by weight; fibrillating the at least one fibrillizable binder in the first mixture by applying a shear force to the first mixture; pressing the first mixture into a first free-standing electrode film; shredding at least a portion of the first free-standing electrode film; preparing a second mixture comprising at least one electrode active material, at least one fibrillizable binder, and the shredded at least a portion of the first freestanding electrode film; fibrillating the at least one fibrillizable binder in the second mixture by applying a shear force to the second mixture; and pressing the second mixture into a second free-standing electrode film; A method comprising:

2. The method of claim 1 , wherein the first mixture comprises at least a portion of a previously fabricated free-standing electrode film.

3. 2. The method of claim 1, wherein the preparing the second mixture comprises mixing the second mixture, and the applying the shear force to the second mixture comprises mixing the second mixture with a shear force greater than the shear force during the preparing.

4. 10. The method of claim 1, wherein the at least one electrode active material of the first mixture comprises one or more electrode active materials selected from the group consisting of lithium metal oxides, carbon-based materials, titanium dioxide, and silicon-based materials.

5. 10. The method of claim 1, wherein the at least one electrode active material of the second mixture comprises one or more electrode active materials selected from the group consisting of lithium metal oxides, carbon-based materials, titanium dioxide, and silicon-based materials.

6. The method of claim 1 , wherein either or both of the first mixture and the second mixture further comprise a conductive material.

7. The method of claim 1 , wherein either or both of the first mixture and the second mixture further comprises a solvent.

8. 8. The method of claim 7, wherein the boiling point of the solvent is less than 180°C.

9. The method of claim 1 , wherein either or both of the first mixture and the second mixture further comprises a solid electrolyte powder.

10. 10. The method of claim 1, wherein the chopped at least portion of the first freestanding electrode film is between 0.1% and 5% by weight of the second mixture.

11. 10. The method of claim 1, wherein the chopped at least portion of the first freestanding electrode film is between 5% and 25% of the second mixture.

12. 10. The method of claim 1, wherein the chopped at least portion of the first freestanding electrode film is between 25% and 50% of the second mixture.

13. 10. The method of claim 1, wherein the chopped at least portion of the first freestanding electrode film is between 50% and 75% of the second mixture.

14. 10. The method of claim 1, wherein the chopped at least portion of the first freestanding electrode film is between 75% and 95% of the second mixture.

15. 10. The method of claim 1, wherein the chopped at least portion of the first freestanding electrode film is greater than 95% of the second mixture.

16. 1. A method of manufacturing an energy storage device, the method comprising: The method of claim 1; and Stacking the second free-standing electrode film on a current collector. A method comprising:

17. 1. A method for manufacturing a free-standing electrode film for an energy storage device, the method comprising: preparing a first mixture comprising at least one electrode active material and at least one fibrillizable binder, wherein the total solids content of the first mixture is greater than 95% by weight; fibrillating the at least one fibrillizable binder in the first mixture by applying a shear force to the first mixture; pressing the first mixture into a first free-standing electrode film; shredding at least a portion of the first free-standing electrode film; preparing a second mixture containing the shredded at least a portion of the first freestanding electrode film; applying a shear force to the second mixture; and pressing the second mixture into a second free-standing electrode film; A method comprising:

18. 20. The method of claim 17, wherein the first mixture comprises at least a portion of a previously fabricated free-standing electrode film.

19. 20. The method of claim 17, wherein the chopped at least portion of the first freestanding electrode film is 100% of the second mixture.

20. 20. The method of claim 17, wherein the chopped at least portion of the first freestanding electrode film comprises only the electrode active material contained in the second mixture.

21. 1. A method of manufacturing an energy storage device, the method comprising: The method of claim 17; and Stacking the second free-standing electrode film on a current collector. A method comprising:

22. A free-standing electrode film for an energy storage device, the free-standing electrode film comprising: at least one electrode active material; and At least one fibrillizable binder Equipped with wherein at least a portion of the at least one electrode active material and at least a portion of the at least one fibrillizable binder are recycled from shredded electrode membranes. Freestanding electrode membrane.

23. 23. The freestanding electrode film of claim 22, wherein the total binder content of the freestanding electrode film is less than 8% by weight of the freestanding electrode film.

24. 23. The freestanding electrode film of claim 22, wherein the total binder content of the freestanding electrode film is less than 4% by weight of the freestanding electrode film.

25. 23. The freestanding electrode film of claim 22, wherein the total binder content of the freestanding electrode film is less than 3% by weight of the freestanding electrode film.

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